1. Field of the Invention
The invention relates to a collision avoidance system that, when an object that approaches from behind a host vehicle, including rear sides, executes driving assistance to avoid a collision with the object.
2. Description of Related Art
There is known a driving assistance technique for, when a vehicle, or the like, (approaching object) that approaches a host vehicle from behind (including rear sides) is detected by a radar provided at the rear end of the host vehicle at the time when the host vehicle is moving backward, avoiding a collision with the approaching object by, for example, issuing an alarm (for example, Japanese Patent Application Publication No. 2013-045142 (JP 2013-045142 A)).
With this technique, for example, when the host vehicle moves backward to exit from a parking space in a state where the host vehicle is parked forward, it is possible to avoid contact, collision, or the like, with an approaching object that is difficult to be visually recognized by a driver due to the presence of another parked vehicle.
However, if a radio wave transmitted from the radar is multiply reflected or diffracted and then received by the radar as a reflected wave, a non-existent approaching object may be detected (hereinafter, such an approaching object is referred to as mirror ghost).
For example, as shown in FIG. 1, if there is a wall or a screen behind a parking space in a state where a host vehicle V is parked backward, a reflected wave from the wall may be multiply reflected from another vehicle, or the like, and received by the radar of the host vehicle V. Then, although there is the wall behind the host vehicle V and no vehicle can approach the host vehicle from the right rear side, the radar may detect a mirror ghost VG that approaches the host vehicle V from the back of the wall.